The present invention relates to a transmission line which has reduced crosstalk and enables the packaging density to be increased over prior lines.
Lines which have heretofore been employed in signal transmission of this type include two-core parallel transmission lines, a twisted pair cable, or a cable composed of these as unit lines. It has therefore not been possible to attain a great reduction in crosstalk together with high packaging density and to obtain favorable flexibility.
As a high-speed and high-density line, for example, a flat cable has been proposed in the specification of Japanese Patent Publication No. 41243/1984. This flat cable is arranged such that ground wires are respectively disposed on both sides of one signal line. these signal and ground lines being alternately knit together by a solid tape, and porous polytetrafluoroethylene tapes are respectively disposed on both sides of the knit lines, and further, a plastic layer is disposed on the respective outer surfaces thereof, thereby forming a flat-cable-shaped transmission line. With this structure, however, it is difficult to increase the density in the lateral direction of the transmission line, and it is not possible to reduce crosstalk by a large margin and to decrease production costs.
The specification of Japanese Utility Model Laid-Open No. 179210/1982 discloses a coaxial conductor flat cable. This construction, however, also involves increased costs.
Accordingly, an object of the present invention is to provide a high-density transmission line which has reduced crosstalk and can be manufactured economically.
Another object of the present invention to provide a transmission line which has reduced crosstalk and makes it possible to satisfactorily obtain the advantages of balanced transmission and also attain an increased packaging density.